Irony certainly can be random or a signifier of implied fate in the case of literary/dramatic irony. Verbal irony, which is closely related to but not identica

Irony certainly can be random or a signifier of implied fate in the case of literary/dramatic irony. Verbal irony, which is closely related to but not identical to sarcasm (though there is quite a lot of debate on exactly the relationship among psycholinguists) is most certainly intentional. "I don't wear my seat belt because if I'm uncomfortable I'll drive more dangerously." "Sounds like you've really thought that one through." Verbal irony, possibly sarcasm depending on whose definition you buy, but definitely intentional in any case. http://en.wikipedia.org/wiki/Irony#Verbal_irony http://en.wikipedia.org/wiki/Irony#Verbal_irony discusses this further and refers to specific research on this topic.